This protocol is investigating different antiretroviral drug regimens in infants and children with HIV-1 infection. Study subjects are those who present to clinic for evaluation of the infection. The drug combinations include zidovudine (AZT, ZDV), didanosine (ddI), zalcitabine (ddC), stavudine (d4T), lamivudine (3TC), nevirapine (Virarume), ritonavir (Norvir), and nelfinavir (Viracept). All drugs except nevirapine and ddC have been FDA approved for use in children. Two hundred children will participate nationwide and 10 children locally. Study endpoints include: a) lack of viral load suppression (RNA PCR), i.e., < 0.75, b) treatment safety, and c) performance of pharmacokinetics (PK) of study drug combinations. Secondary endpoints include study of specific characteristics of HIV RNA changes (slope, nadir, AUC, etc.), CD4 change, weight change, population PK and survival comparisons.